Symbols that only have property lists

Some symbols, like `default-button` and the symbols created by `define-button-type`, only have plists, and I couldn't find any functions in helpful to inspect them. Does helpful already have a way to inspect them? How? If not, would that be hard to add?

Thanks in advance, cheers, etc! =)
Eduardo Ochs
http://anggtwu.net/#eev
